Method and system for contactless vital sign monitoring via calculating displacement signal by applying adaptive nonlinear least squares method

Patent metadata

Field	Value
Publication number	US-12465234-B2
Application number	US-202318879775-A
Country	US
Kind code	B2
Filing date	Jun 27, 2023
Priority date	Jun 30, 2022
Publication date	Nov 11, 2025
Grant date	Nov 11, 2025

Abstract

A method for vital sign monitoring using a radar sensor system that includes a transmitter, a receiver, and processing device. The transmitter irradiates a body region of a person with radar radiation, the receiver generates a receiver signal from reflected radiation from the body region, and the processing device generates, for each of a plurality of processing windows, a displacement signal based on the receiver signal. The displacement signal characterizes a body motion having, as oscillating motions, a breathing motion and a heartbeat motion, and calculates an estimated fundamental frequency for at least one oscillating motion. The processing device applies an adaptive Nonlinear Least Squares method to calculate a plurality of frequency estimates, each of which corresponds to one of a plurality of harmonics of a first oscillating motion, wherein the processing device calculates a first estimated fundamental frequency for the first oscillating motion based on the frequency estimates.

First claim

The invention claimed is:

1 . A method for vital sign monitoring using a radar sensor system,
the radar sensor system comprising a transmitter, a receiver and processing device, wherein:
the transmitter irradiates at least one body region of an object with radar radiation;
the receiver generates a receiver signal from reflected radiation from the at least one body
region; and
the processing device generates, for each of a plurality of processing windows that represent time intervals, a displacement signal based on the receiver signal, which displacement signal characterizes a body motion comprising, as oscillating motions, a breathing motion and a heartbeat motion, and calculates an estimated fundamental frequency for at least one oscillating motion,
wherein the processing device combines single-bin displacement signals from a plurality of position bins, depending on a correlation of these single-bin displacement signals, to obtain an aggregate displacement signal, wherein the processing device, based on the aggregate displacement signal, applies an adaptive Nonlinear Least Squares method to calculate a plurality of frequency estimates, each of which corresponds to one of a plurality of harmonics of a first oscillating motion, and wherein the processing device uses an individual search region for each frequency estimate, adapts at least one search region for at least one processing window, and calculates a first estimated fundamental frequency for the first oscillating motion based on the frequency estimates wherein at least one of the breathing motion or the heartbeat motion of the object is monitored.

2 . The method according to claim 1 , wherein the processing device uses at least one search region for a fundamental frequency and at least one different search region for a higher harmonic.

3 . The method according to claim 1 , wherein the first oscillating motion is the heartbeat motion.

4 . The method according to claim 1 , wherein the processing device calculates the first estimated fundamental frequency so that it corresponds to one of the frequency estimates.

5 . The method according to claim 1 , wherein the processing device generates an in-phase signal and a quadrature signal based on the receiver signal.

6 . The method according to claim 1 , wherein the processing device performs an at least one-dimensional discrete Fourier transform based on the in-phase signal and the quadrature signal to obtain a slow-time signal for each of a plurality of position bins, each of the position bins corresponding to an at least one-dimensional position relative to the transmitter.

7 . The method according to claim 1 , wherein the processing device performs a complex phase demodulation on the slow-time signal of each position bin to retrieve a single-bin displacement signal for the respective position bin.

8 . The method according to claim 1 , wherein the adaptive Nonlinear Least Squares method is based on minimization of a difference between the aggregate displacement signal and a model function with a plurality of harmonics for each of at least one oscillating motion.

9 . The method according to claim 1 , wherein the processing device calculates at least one frequency of one oscillating motion using a cost function that is based on a Fast Fourier Transformation of the aggregate displacement signal.

10 . The method according to claim 1 , wherein the processing device uses a Kalman filter to determine the first estimated fundamental frequency.

11 . The method according to claim 1 , wherein the processing device uses an estimated fundamental frequency calculated in one processing window to define a search region for a frequency in a later processing window.

12 . The method according to claim 1 , wherein the processing device calculates, for at least one processing window, a predicted state comprising a predicted fundamental frequency that is based on at least one previous processing window, and selects one frequency estimate as the estimated fundamental frequency depending on a comparison between the predicted fundamental frequency and the frequency estimate.

13 . A radar sensor system for life sign monitoring, comprising:
a transmitter for irradiating at least one body region of an object with radar radiation; a receiver for generating a receiver signal from reflected radiation from the at least one body region; and a processing device adapted to combine single-bin displacement signals from a plurality of position bins, depending on a correlation of these single-bin displacement signals, to obtain an aggregate displacement signal, to generate, for each of a plurality of processing windows that represent time intervals, a displacement signal based on the receiver signal, which displacement signal characterizes a body motion comprising as oscillating motions a breathing motion and a heartbeat motion, and to calculate an estimated fundamental frequency for at least one oscillating motion, wherein the processing device is adapted to apply, based on the displacement signal, an adaptive Nonlinear Least Squares method to calculate a plurality of frequency estimates, each of which corresponds to one of a plurality of harmonics of a first oscillating motion, wherein the processing device is adapted to use an individual search region for each frequency estimate, to adapt at least one search region for at least one processing window, and to calculate a first estimated fundamental frequency for the first oscillating motion based on the frequency estimates.

Assignees

• Iee Sa
• Univ Luxembourg

Inventors

• Tedgue Beltrao Gabriel
• Alves Martins Wallace
• Mysore Rama Rao Bhavani Shankar
• Alaeekerahroodi Mohammad
• Schröder Udo
• Tatarinov Dimitri

Classifications

• A61B5/7275

  Determining trends in physiological measurement data; Predicting development of a medical condition based on physiological measurements, e.g. determining a risk factor · CPC title

• A61B5/7257

  using Fourier transforms · CPC title

• A61B5/725

  using specific filters therefor, e.g. Kalman or adaptive filters (specific diagnostics methods using using bioelectric or biomagnetic signals A61B5/316) · CPC title

• A61B5/7228

  Signal modulation applied to the input signal sent to patient or subject; Demodulation to recover the physiological signal · CPC title

• A61B5/113

  occurring during breathing · CPC title